\[\left( 6\frac{8^{\backslash 3}}{15} - 4\frac{21}{45} \right) \cdot 4,5 - 2\frac{1}{6}\ :0,52 =\]
\[= \left( 6\frac{24}{45} - 4\frac{21}{45} \right) \cdot \frac{45}{10} - \frac{13}{6}\ :\frac{52}{100} =\]
\[= 2\frac{24 - 21}{45} \cdot \frac{45}{10} - \frac{13}{6} \cdot \frac{25}{13} =\]
\[= 2\frac{3}{45} \cdot \frac{45}{10} - \frac{13 \cdot 25}{6 \cdot 13} =\]
\[= \frac{93}{45} \cdot \frac{45}{10} - \frac{25}{6} =\]
\[= \frac{93^{\backslash 3}}{10} - \frac{25^{\backslash 5}}{6} = \frac{279}{30} - \frac{125}{30} =\]
\[= \frac{279 - 125}{30} = \frac{154}{30} =\]
\[= 5\frac{4}{30} = 5\frac{2}{15}\]